Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INV:ENTION
The present invention relates -to an lmprovement in the
shaping oE slit segments of meshes formed in deformable strip
and, in particular, relates to an improvement in the method and
apparatus of copending Canadian Patent Application No. 315,190
filed October 31, 1978 wherein a concurrent slitting and preforrn-
ing operation provides a plurality of longi-tudinally extending
strand-like components comprising segments elongated by deforma-
tion out of the plane of the strip and unslit segments retained
in the plane of the strip. The unslit segments together define
continuous bands extending laterally across the portion of strip
contained between longitudinally extending edge portions of
strip. In a second slit-ting step, the slits are extended in a
staggered relation to permit lateral expansion of the slit
portion of the strip. Opposite longitudinally extending edges
of the strip are then drawn apart to expand the slit and pre-
formed strip to form sheet having a network of meshes which are
substantially in the plane of the sheet. Because of the holding
of the bands containlng all the bonds which connect adjacent
components during slit segment elongation, desired elongation of
the slit segments as they are formed is achieved while rupture
of the strands during mesh expansion or failure of the strands
at node bonds is substantially avoided.
In known methods for elongating slit segments so that
mesh areas do not become shorter than unslit borders on lateral
expansion, e.g. the preforming of wires from strip having
conventionally staggered rows of slit as in U.S. Patent 1,212,963,
the wires are shaped against symmetrically contoured tool faces.
This patent is di:rected to the production of metal lath, and it
is unlikely that stretching of the wires during preformlng of
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metal suitable for this purpose would cause localized weakening
that may afEect their usefulness.
STATEMENT OF INVENTION
In the preforming of slit segments of materials having
low tensile strengths, e.g. lead or lead alloys, we have observed
that areas of weakness occur near the trailing ends of slit
segments as the strip is advanced at high speeds through the
slitting and preforming assembly. We have determined that the
slit segments are more uniformly stressed if substantially
convexly shaped tool surfaces used to deform slit segments out of
the plane of the strip are asymmetrically shaped with the
distances between their apices and their respective leading ends
which enter the strip being less than the distances between their
apices and their trailing ends.
The method of our invention for forming elongated slit
segments in deformable strip comprises, in general, concurrently
slitting and preforming said strip by intermeshing, substantially
convexly shaped tool surfaces each having a linear leading
portion and a linear trailing portion joined by a rounded apex
portion, said linear leading and trailing portions collinear with
and generally defining portions of the sides of a triangle having
a base wherein said base has a length equal to the length of the
strip being slit and the length of the side of the triangle
corresponding to and collinear with the leading portlon is not
greater than the length of the side of the triangle corresponding
to and collinear with the trailing portion and the angle formed
between the side of the triangle corresponding to the leading
portion and the base is not greater than 90.
More preferably, the length of the linear leading
portion is less than the length of the linear trailing portion
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within -the range of relative ratios of l::L to 1:10 and the
angle formed between the side of the triangle corresponding to
the leading portion relative to the base is in the,ranye of
from about 30 to about 85~
The apparatus of our invention comprises a pair of
opposed rolls each having a plurality of equispaced discs having
circumferential, equally spaced, convexly shaped tool surfaces
alternating with substantially flat surfaces whereby peripheral
surfaces of opposing rolls are adapted to interact on strip
passing therebetween to slit and preform segments in said strip
by intermeshing of said convexly shaped tool surfaces and define
continuous lateral unslit bands by said substantially flat
surfaces, said convexly shaped tool surfaces each having a
linear leading portion and a linear trailing portion joined by
a rounded apex portion, said linear leading and trailing portions
collinear with and generally defining the sides of a triangle
having a base wherein said base has a length equal to the length
of the strip being slit and the length of the side of the
triangle corresponding to and collinear with the lead;ng portion
is not greater than the length of the,side of the triangle
corresponding to and collinear with the trailing portion and the
angle formed between the side of the triangle corresponding to
the leading portion and the base is not greater than 90.
BRIEF DESCRIPTION OF THE DRAWINGS
Development of preferred tool surface shapes will now
be described in detall, reference being made to the accompanying
drawings, wherein:
Figure 1 is a side elevation showing engagement of
slitting and preforming rolls of the inven-
tion used to proyide elongated slit segments;
Figure 2 is a plan o:E the slitting and preforming
rolls of Fiyure 1 showlng strip after
passing therethrough;
Figure 3 is a perspective view, par-tly cut away,
of the said stri.p as it leaves the sli-tting
and preforming rolls of Figures l and 2;
Figure 4 is a plan of apparatus used to simul.ate, on
an enlarged scale, movement of deforrnable
plastic strip through slitting and
preforming rolls wherein one tool surface
modification is shown;
Figures 5 to 13 are plans of proportionately enlarged
tooled peripheral surfaces used in the
apparatus of Figure ~ and outlines of
deformed plastic strip provided thereby
wherein:
Figure 5 relates to a symmetrical circle-based
tool surface;
- Figure 6 relates to a rectangle-based tool surface;
Figure 7 relates to a modified rectangle-based
tool surface;
Figure 8 relates to a first modification of a
symmetrical triangle-based tool surface;
Figure 9 relates to a second modification of a
symmetrical triangle-based tool surface;
Figure lO relates to a first modification of an
asymmetrical triangle-based tool surface;
Figure ll relates to a second modification of an
asymmetrical triangle-based tool surface;
Figure 12 relates to a third modification.. of an
asymmetrical triangle-based tool surface;
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Figure 13 relates -to a fourth modification of an
asymmetrical triangle-based tool surface;
Figures 14 to 17 are outlines of deformed plastic s-trip
formed by inverting tool portions of the
apparatus of Figure 4 to observe the effec-ts
of reverse rotation of the tool surEaces of
Figures 10 to 13, respectively; and
Figure 18 geometrically i:Llustrates a triangle incorpo-
rating the components oE a tool surface
employed according to -the method and apparatus
of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in Figures 1 and 2, strip 10 passes between
coacting rolls 12 and 14. Each roll has a plurality of spaced
discs 16, each disc having tooled peripheral surfaces comprising
alternating relatively flat equispaced portions 18 and substantial-
ly convexly shaped portions 20. As the discs rotate, flat portions
18 engage strip 10 to hold strip bands 22 extending between a
central portion 24 of the strlp and lateral portions 26 in the
plane of the strip while substantially convex]y shaped tool
surface portions 20 intermesh and overlap to slit areas 28~
.
which are between bands 22, and deform segments 30 which are
between pairs of slits 32 out of the plane of the strip. Slit
segments 30 are elongated an amount sufficient to compensate for
shortening of mesh portions 34 which contain -the slit segments as
slits 32 are extended in a staggered relation and lateral portions
26 of the strip are moved apart in subsequent steps, as disclosed
in copending Canaclian Patent Application No~ 315,190, to provide
open meshes in the plane of the strip. The amount of elongation
required depends on the size of the slit end angles required in
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the open meshes. For example, for sl.it end angles of 70 for
typical battery grids, elongations of about 22 percent are
required. Therefore, the lengths of tool surfaces 20 used in
the following tests were 22 percent greater than the length of
material being sl.it in areas 28, ~nless otherwise noted.
Preliminary tests in the slitting and preformi.ng of
strip and in the lateral expansion of this strip -to form expanded
mesh sheet indicated that less damage to slit segments and
connecting nodes occurred when the substantially convexly shaped
portions 20 of the tooled peripheral surfaces of spaced discs 16
were asymmetrically shaped with their apices in advance of the
centre line between the entry and trailing ends of tool faces 20,
i.e., closer to the leading ends than to the trailing ends of the
tool faces. In order to define more clearly the form of this
asymmetry, test apparatus 36, Figure 4, was made to determine on
an enlarged scale the effects on slit and preformed strip of
tool surfaces having different shapes. Circle-, rectangle- and
triangle-based shapes were tested. Linear dimensions were
enlarged to five times those of discs 16 when used to slit and
preform 1.27 mm thick metal strip.
For each.shape shown in Figures 5 to 13, three pieces
of 6.35 .mm thick hard plastic sheet were prepared with each
having three lobes 38 with tooled surfaces corresponding to
convexly shaped portions 20 spaced by two node areas 40
corresponding to relatively flat portions 18 of the peripheral
surfaces of discs 16. Two pieces 41 and 42 were bolted together
with the prepared faces aligned and with a 6.35 mm spacer in
between to provide an assembly 43 which simulates a pair of
adjacent discs 16 of roll 12 and which was adapted to rotate
about centre 44. The third piece, 46, having a support space of
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6.35 mm thickness, not shown, was adapted -to rota-te about centre
48 with its lobes 38 moving in circumferential alignrnent between
corresponding lobes 38 of the pieces of sheet making up assembly
43. Centres 44 and 48 were spaced to permit 6.35 mm thick
extruded plasticine strip to be passed through the opening between
engaging faces of assembly 43 and piece 46, with flat surEaces 40
holding portions of the strip corresponding to bands 22 as lobes
38 engaged to slit and preform portions corresponding to portions
28 between bands 22. For convenience, the apparatus was mounted
on a table to provide support for the plasticine strip and to
permit horizontal rotation during slitting and preforming. In
Figure 4, formation of elongated segments 49 by action of lower
piece 42 of assembly 43 and formation of an adjacent, overlying
line of elongated segments 50 by action oE piece 46 are shown.
For clarity of illustration, elongated segments 49 formed by
partially cut away upper piece 41 are not shown. Synchronization
of the rotation of assembly 43 and piece 46 was facilitated by
inscribing equally spaced radial lines 51 on each and maintain-
ing circumferential alignment of corresponding lines during
rotation. Figure 4 illustrates apparatus 36 wherein the asymmet-
rical triangle-based tool faces of Figure 10 were used. Like
apparatus with corresponding tool faces was used for each of
the shapes shown in Figures 5 to 13. Reference will now be made
to each of the lobe shapes tested and to corresponding elongated
segments of plasticine. In Table 1, dimensions chosen for tool
lobes were based on slitting and preforming of 8.81 mm wide
areas 28 spaced between 3.18 mm wide bands 22 of strip 10.
Unless otherwise stated, the length of the preforming face
extending from the leading end to the trailing end of each lobe
38 was 122 percent of 8.81 mm. This length comprised the sum of
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the lengths of any curved or linear parts. Curved por-tions
were arcs of circles having arbitrarily chosen radii as shown
in Table 1. Dimensions were determined mathematically with
computer aid in the solution of more complex equations~ to be
described below. These dimensions were multiplied by 5 to get
the dimensions used in the test apparatus, i.e., the peripheral
surfaces had flat 15.90 mm long node portions 40 spaced by 44.05
mm long chords, the ends of which were the leading and trailing
ends of preforming lobes 38.
Table 1
.
Lobe Shapes Studied
Triangle
Arc Radii Side Ratio
Figure Basic Shape nescriptiOn _ mm le~
circle arc - 5.02
6 rectangle symmetrical 1.70
7 rectangle one arc, one slope 1.70
8 triangle symmetrical 1.98 1:1
9 triangle symmetrical 3.18 1:1
triangle asymmetrical 1.98 1:1.5
11 triangle asymmetrical 3.97 1:].. 5
12 triangle asymmetrical 1.98 1:2.5
13 triangle asymmetrical 3.18 1:2.0
l4 triangle asy~metrical 1.98 1.5:1
triangle asymmetrical 3.97 1.5:1
16 triangle asymmetrical 1.98 2.5:l
17 triangle asymmetrical 3.18 2.0:1
In the test illustrated by Figure 5, preforming lobe 52
was a segment of a circle wherein arc 54 was 22 percent longer
than chord 56 which represents, on an enlarged scale, the 44.05
mm length of material from which elongated segment 58 was formed
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from plasticine strip 60. Trailing end 62 of segment 58 shows
more thinning than the remaining part of the segment. This is
typical when slitting and preforming are done with rolls having
circle-based lobes.
In the test illustrated by Figure 6, lobe 82 was based
on a rectangle having base 84 corresponding to the width of area
28 being slit. Tool surface 86, having a length 22 percent
longer than base 84, comprised linear portion ~ on the opposite
side of the rectangle and two circular end portions 90 which were
shaped to approach the rectangle sides tangentially. Portions of
the rectangle not comprising tool surface 86 are shown by broken
lines. Excessive localized thinning occurred in trailiny portion
92 of elongated segment 94 of strip 96.
Figure 7 shows a modified rectangle-based lobe 98
wherein the trailing circle segment of ~igure 6 was replaced by
a 45 bevelled portion 100. Tool surface 102, comprising arc
portion 104, linear portion 106 and bevelled portion 100 was
only 119 percent of the length of base 108. Localized thinning
as shown in trailing portion 110 of elongated segment 112 of
strip 114 was not as great as with the circular trailing segment
formed by lobe 82.
Lobe 116 of Figure 8 was based on a symmetrical
triangle wherein base 118 was 44.06 mm, the length of
plasticine strip being slit. Linear portions 120 of slitting
and preforming face 122 were joined by a circular apex portion
124 which met the linear portions tangentially. ~xtension of
linear portions 120, by broken lines, to ver-tex 126 completes
the triangle. The radius of apex portion 124 was 9.90 mm, i.e.,
5 times the radius shown in Table 1 for the shaping of lead
3Q strip. Trailing portion 128 of elongated segment 130 of
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plasticine strip 132 showed greater thinning than thé rest of
the segment.
Lobe 134 of Figure 9 was also based on a symmetrical
triangle, with line 136 representing the length of material being
slit. Linear portions 138 of slitting and preforming face 140
were joined by circular apex portion 142 which met the linear
portions tangentially. Broken lines meeting at vertex 144
complete the triangle. In this example, the radius of apex
portion 142 was 15.90 mm, i.e., greater than that shown in Figure
8. Trailing portion 146 of elongated segment 148 of strip 150
showed less uniform distribution of thinning along the length of
the trailing portion of segment 148 than was obtained with the
smaller radius apex shown in Figure 8.
Figures 10 to 13 represent tests with a group of four
triangle-based lobes having slitting and preforming surfaces
comprising linear leading and trailing portions which were parts
of sides of asymmetrical triangles and circular arc portions
meeting the linear portions tangentially near the triangle
vertex at which the sides intersected. Tests were made with
three triangle side ratios wherein the ratios of leading side of
triangle to trailing side of triangle < 1:1.
Three circular arc radii were also tested. Because
of this asymmetry, the apex of each lobe was in advance of the
centre line between the leading and trailing ends of the lobe,
i.e., the apex was closer to the leading end than to the trailing
end of the lobe.
In lobe 152 of Figure 10, triangle base 154 was 44.6 mm,
the length of plasticine strip being slit. Leading linear portion
156 of slitting and preforming face 158 was shorter than trailing
linear portion 160, their lengths being fixed by the length of
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base 154, predetermined 22 percent e]ongation, a se]ected ra-tio
of leading side -to trailing side equal to 1:1.5 for -the corres-
poinding collinear sides of the triangle having vertex 162, and
choice of a circular arc apex portion 164 having a 9.92 mm radius.
This radius was about 23 percent ol the length of base 154. Apex
164 was in advance of centre line 166 between the leading and
trailing ends of the lobe. With this shape, more uniform thinniny
of preformed segment 168 oE strip 170 was obtained than with al]
the other shapes tested. It may be noted that trailing portion
172 was generally uniformly thinned throughout its length, with
slightly greater thinning in central part 174.
In lobe 176 of Figure 11, -triangle base 178 was the
length of plasticine strip being slit. Leading linear portion
180 and trailing linear portion 182 of slitting and preforming
face 184 were collinear with the sides of a triangle intersecting
at vertex 186 and having base 178. As in Figure 10, the ratio of
the lengths of the sides of this triangle was 1:1.5. However,
the radius of circular arc apex portion 188 was 19.85 mm, twice
that of the arc of the Figure 10 lobe and about 45 percent of the
length of -triangle base 1780 As before, triangle vertex 186 and
the apex of arc 188 were in advance of centre line 190. Severe
thinning of preformed slit segment 192 of strip 194 occurred at
the leading end, i.e., in portion 196. This thinning will be
discussed after Figures 12 and 13 are described.
In lobe 198 of Figure 12, triangle base 200 was the
length of material being slit. Leading linear portion 202 and
trailing linear portion 204 of slitting and preforming face 206
were collinear with the sides of a triangle intersecting at
vertex 208 and having base 200. The ]engths of the sides of the
triangle were in the ratio of leading side to trailing side equal
7~
-to 1:2.5. The radius of circular arc apex 210 was 9.92 mm, the
same as in Figure 10. Triangle vertex 208 and the apex of arc
210 were in advance of centre line 212. More thinning of
corresponding slit segment 214 of strip 216 occurred at the
leading end, i.e., in part 218, than in the rest of the segment.
In lobe 220 of Figure 13, triangle base 222 was the
length of material beiny slit. Leading linear portion 224 and
trailing linear portion 226 of slitting and preforming face 228
were collinear with sides oE a triangle intersecting at ver-tex
230 and having base 222. The lengths of the sides of the
triangle were in the ratio of leading side to trailing side equàl
to 1:2Ø The radius of circular arc apex portion 232 was 15.88
mm, i.e., intennediate the 9.92 mm and 19.84 mm radii of the arc
portions of Figures 10 and 11, respectively. The radius was
about 36 percent of the length of triangle base 222. Triangle
yertex 230 and the apéx of arc 232 were in advance of centre
line 234. ~s in Figures 11 and 12, most of the thinning of
corresponding slit segment 236 of strip 238 occurred at its
leading end, in portion 240. Comparison of Figures 11, 12 and 13
indicates that leading end thinning becomes more severe as the
radius of the lobe apex increases.
Figures 14 to 17 illustrate slit and preformed segments
obtained by reversing the direction of rotation of the parts of
apparatus 36, with the effect that trailing portions shown in
Figures 10 to 13 became leading portions. For convenient compari-
son with Figures 10 to 13, the drawings are rotated so that the
portions of strip formed by the leading ends of the lobes are to
the right. Tool lobes, being the same as in Figures 10, 11, 12
and 13 respectively, are not shown in Figures 14, 15, 16 and 17.
All the drawings illustrate rotation which provides left to right
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movement of the lobes in the engagernent axea with left to right
movement of strip between lobes. I.obe data for this reverse
shaping of slit segments are given in the table. In each case
severe thinning occurred at the trailing end of the segment.
Elongated segments 242, 248, 254 and 260 of strips 2~, 250, 256
and 262 showed excessively thin portions 2~6, 252, 258 and 264.
Increasing the leading end to trai]ing end ratio and increasing
the radius of the apex both contributed to more severe localized
thinning.
It will be understood that the preceding description
and data pertaining to the ratios of the length of the side of
the triangle corresponding to the linear leading portion of the
tool surface relative to the linear trailing portion relate to
a 22 percent elongation of slit segments and it is understood
that preferred ratios can vary according to desired percentage
elongation, characteristics of the metal alloy formed such as
hardness and tensile strength, and thickness of the metal strip.
We have found that a range of ratios of from l:l to 1:10 is
satisfactory for elongations such as 5 percent elongation of
lead alloy slit segments with, for example, a leading angle of
about 65 between the triangle side collinear with the leading
linear portion of the tool surface and the triangle base. In
order to provide greater elongations of lead alloy slit segments,
e.g., up to about 30 percent, asymmetrical shaping of the lobes
using a ratio which is less than 1:1 but not less than about
1:5 is preferred. The leading angle may be in the range 30 to
85
Although we are not bound by hypothetical considera-
tions, we believe the relationship of leading angle, ratio of
leading portion of triangle to trailing portion of triangle and
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radius of curve at the apex oE the triang]e relative to percent
elongation can be expressed for triangular based tool shapes,
with re~erence to Figure 18, as follows:
%E = (AE + hF are -~ FC) _ AC x 100 (1)
AC AC
cos a ~ + tan a~ ~~ cos e---fl + -tan e~ 2 r an ~ )
tan e~ ~ tan a/
= AC (1 + T~) (2)
e = sin~l ~ sin a~
wherein:
%E = pereent elongation
AC = slit length
a = leading angle
c = trailing angle
r = radius of curve at apex of triangle
BC ~ ratio of leading portion of triangle
to trailing portion of triangle
The values of angles "a" and "e" can be ealeulated
from equations (2) and (3) for various combinations of %E, AC,
r and the ratio AB
BC
Although mueh of the data was obtained from tests in `
whieh plasticine strip was used, comparative tests between
plastieine and lead alloy conventionally used for battery grids,
eontaining, e.g., 0.6% tin, 0.06% calcium and the balance lead,
established that both materials functioned in the same manner
within the scope of the tests.
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The method ana apparatus of the present invention have
a number of impor-tant advantages as evidenced by the following
conclusions which have been drawn from the foregoing data.
1. Use of symmetrical triangle-based slitting and preforming
lobes with convexly curved apices produces more uniformly
elongated segments than use of lobes which are arcs of
circles.
2. Use of symmetrical rectangle-based lobes with convexly
curved leading and trailing ends leads to excessive
thinning at the trailing ends of segments. Provision of
a linear tapered section at the trailing end decreases
the thinning of elongated segments at this end.
3. Use of an asymmetrical triangle-based lobe having a
convexly curved apex wherein the ratio of the length of
the side of the triangle which is collinear with the
leading linear portion of the lobe to the length of the
side of the triangle which is collinear with the trailing
; linear portion of the lobe is greater than 1:1 leads to
excessive thinning at the trailing end of an elongated
segment.
4. Use of a preferred asymmetrical triangle-based lobe having
a convexly curved apex wherein the ratio of the length of
the side of the triangle which is collinear with the
leading linear portion of the lobe to the length of the
side which is collinear with the trailing portion of the
lobe is less than 1:1 results in less trailing end
thinning than that obtained with sy~netrical triangle-
based lobes. Use of symmetrical triangle-based lobes, i.e.,
a 1;1 ratio, results in less localized trailing end thinning
than use of arcuate or semicircular lobes.
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5. In the preferred configuration described above, a lobe
having an apex with a small radius of curvature, e.g.,
the lobes of Figures 10 and 12, provides better
distribution of elongation over the length of a
segment than does a lobe wherein the radius of curva-
ture of the apex is relatively large, e.g., the lobes
of Figures 11 and 13. This radius, which is less than
about half the chord representing the length of strip
being slit to provide linear lobe portions, should not
be decreased to such an extent that breakage of slit
segments due to sharp bending is likely to occur.
6. It is evident that, as the ratio decreases, the angle
formed between the side of the triangle corresponding
to the linear leading portion and the base approaches
90. Also, as the length of the portion of the leading
side of the triangle which comprises the leading
linear portion of the lobe approaches zero, the lobe
approaches a limiting shape resembling half a tear
drop wherein the leading end of the rounded apex
portion tangentially meets the leading end of the base
substantially at 90. Since, in the preferred
asymmetrical triangle-based lobe described above, some
thinning at the leading end of an elongated segment
occurred with a 1:2.5 ratio, it is preferred that this
ratio be not less than about 1:5. It is evident from
Figures 11 - 13 that choice of small ratio should be
accompanied by choice of an apex having a small radius
of curvature.
; 7. In the said preferred configuration, the optimum lobe
has a triangle side ratio of leading end to trailing
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end which is about 1:1.5 and also has a small radius
of curvature in the convexly curved apex portion.
In general, slitting and preforming to provide meshes
with elongated segments having most uniform thickness throughout
their length is effected by use of rotating discs provided with
asymmetrical triangle-based lobes having linear leading and
trailing portions spaced by convexly curved apices wherein, in
each lobe, the ratio of th~ length of the side of the triangle
which is collinear with the leading linear portion to the length
1~ of the side of the triangle which is collinear with the trailing
linear portion is less than 1:1. More uniform thinning is
achieved be-tween the apex of a preformed segment and its trailing
end than is obtained with lobes having correspondiny side ratios
equal to or greater than 1:1 as shown in Figures S and 14 to 17.
It is also desirable that the radius of curvature of the curved
apex be small, thereby providing a curved apex portion which is
relatively short when compared to the combined lengths of the
linear portions. Since initiation of some localized excess
thinning at the leading end occurs when the ratio is decreased
to 1:2.5, a ratio between 1:1 and 1:2.5 is preferred for 22~
elongation. This thinning is due at least in part to choice of
; an apex having a relatively large radius.
With the formation of uniformly thinned elongated
; segments during the slitting and preforming of lead or lead
alloy strip prior to lateral expansion to provide a network of
meshes suitable for battery grids, the slitting and preforming
operation and the lateral expansion can be carried out at
relatively high speeds. For example, by the use of preferred
asymmetrical triangle-based lobes as described to provide
22 percent elongation expanded mesh sheet was made from 1.27 mm
thick strip at a rate of 58 metres per minute with substantially
no breakaye of elongated wires.
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